Production of sulphonation derivatives



UNITED STATES PATENT OFFICE PRODUCTION OF SULPHONATION DERIVATIVES Wendell W. Meyer, Decatur, Iil., assignor to The Solvay Process Company, New York, N. Y., a corporation of New York No Drawing. Application September 12, 1938, Serial No. 229,538

11 Claims.

acids which may be carried out emciently on a commercial scale.

A further object of the invention is to provide a process for the production of alpha-sulphonic acid derivatives of saturated higher fatty acids, which derivatives are characterized by a good color and are valuable for use as detergents and wetting, emulsifying, and the like agents.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

It has been discovered in accordance with the present invention that by sulphonating the lower alkyl esters of saturated higher fatty acids with sulphur trioxide in the presence of liquid sulphur dioxide, it is possible to prepare alpha-sulphonic acid derivatives of the saturated higher fatty acids from which the esters are obtainable. For example, it has been found that by sulphonating the methyl ester of lauric acid in this way, the alpha-suiphonic acid derivative of lauric acid is produced rather than the sulphonation derivative of the ester itself. as might be expected.

The preparation of alpha-sulphonic acid derivatives of saturated higher fatty acids by sulphonating the lower akyl esters of such acids has been found to possess several advantages over a process in which the free acids are sulphonated in this way. Thus, when sulphonating a lower alkyl ester of a saturated higher fatty acid containing a certain amount of esters of unsaturated higher fatty acids, products of better color are obtained than when sulphonating a saturated higher fatty acid containing the same amount of unsaturated higher fatty acids. While the reason for this result is not thoroughly understood, it appears that unsaturated fatty acids in the form of their esters are less drastically affected by suphonations carried out with sulphur trioxide in the presence of liquid sulphur dioxide than the free acids. For this reason, when a saturated higher fatty acid ester is employed as starting material, it can contain a larger proportion of unsaturated higher fatty acid bodies (esters) than in the case of the free fatty acids. Thus, I have found that products of good quality can be obtained by sulphonating esters of saturated higher fatty acids which contain up to ten per cent by weight of esters of unsaturated higher fatty acids. However, it is generally preferable to use as starting materials esters of saturated higher fatty acids which contain less than five per cent, and especially less than two per cent. by weight of esters of unsaturated higher fatty acids. Further, as compared with the sulphonation of free saturated higher fatty acids, the amount of water which can be tolerated in the sulphonation reaction mixture is greater. It is preferred, however, to carry out the sulphonation in the presence of not more than three per cent of water based on the weight of sulphur trioxide used in the reaction mixture.

Also. for optimum results, the reaction is carried out under substantially anhydrous conditions; i. e., in reaction mixtures containing not more than one per cent of water based on the weight of sulphur trioxide used.

From another viewpoint, it is surprising that go this process is productive of the results noted since the usual sulphonating procedures, if applied to the sulphonation of esters of saturated higher fatty acids, are unsatisfactory because they result in a small degree of sulphonation or in the production of dark-colored products. If oleum, concentrated sulphuric acid. or chlorsulphonic acid is used in the sulphonation, significant yields of sulphonation products are not obtained at low temperatures, while at high temperatures serious carbonization of the organic material occurs. In the cases of the first two of these sulphonating agents, the results appear to be due to the fact that water (as H1804) is present in the reaction mixture which is deleterious. In the case of chlorsulphonic acid, hydrochloric acid is formed which must be removed.

The alpha-sulphonic acid derivatives of saturated higher fatty acids prepared by the present process constitute valuable'detergent, wetting, 40

and the like agents which are active in hard water and in acid and alkaline solutions. Thus, as compared with ordinary soaps, they are not hydrolyzed to the free fatty acids in acid solutions. Also, they do not have the disadvantage of soaps of being precipitated in the form of sticky curds from solutions containing calcium or magnesium salts which have no detergent value, but which constitute impurities. As compared with ordinary sulphonated fatty acids obtained by the sulphonation of unsaturated and/or hydroxy fatty acids, of which the Turkey red oils are outstanding examples, the derivatives possess considerably superior wetting and detergent properties and are more stable against hydrolysis. The properties of the derivatives. as compared with the properties of ordinary sulphpnated'fatty acids, appear to be due to the facts that the sulphonic acid group in the derivatives is at the end of a long carbon chain, and they contain a sulphonic acid group rather than the more easily hydrolyzed sulphuric acid ester group.

The starting material employed in the present process may be any lower alkyl ester of a saturated higher fatty acid or a mixture of such esters. Thus, the esters obtainable by esterifying a saturated higher fatty acid with a lower monohydric alcohol, such as, for example, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, and isobutyl alcohol, are adapted for use in this connection. Although the alcohols employed should contain only one hydroxyl group, since otherwise sulphation of a hydroxyl group occurs, as distinguished from sulphonaticn; of the fatty acid radical of the esters, the alcohols may con tain substituents which do not interfere with the sulphonation reaction. Bubstituents which may be mentioned, by way of example, are: methoxy, ethoxy, and dimethyl amino radicals. The term "saturated higher fatty acid is intended to denote any saturated fatty acid which contains at least 8 carbon atoms and which is free from. hydroxyl groups. The more valuable products are obtained in accordance with the present invention from esters of saturated higher fatty acids which contain from 8 to 24, and especially from 14 to 18, carbon atoms. Examples of such fatty acids are the following: myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid.

The process is preferably carried out using lower allnvl esters of saturated higher fatty acids derived; from naturally occurring fats or oils of which tallow, cocoanut oil, babassu oil, palm oil, and fish oils; e. g., menhaden fish oil, are examples, as starting materials. The naturally occurring fats or oils may be used as the initial starting materials in the process. In this case it is advisable to subject them to hydrogenation as the first step in the process. As is well known, the naturally occurring fats and oils are composed of glycerides of unsaturated as well as saturated higher fatty acids: tallow, for example, contains glycerides of the saturated fatty acids, stearic acid, palmitic acid, and myristic acid; and glycerides of the unsaturated fatty acids, oleic acid and linoleic acid. The hydrogenation of a fat or oil is preferably effected by contacting the material with hydrogen at an elevated tempera ture and at a superatmospheric pressure in the presence of a hydrogenation catalyst, such as nickel. The product obtained as a result of this treatment is composed substantially entirely of glycerides of saturated fatty acids.

The hydrogenated fat or oil may be converted to lower alkyl esters of saturated higher fatty acids by first hydrolyzing it to the free acids and glycerine, and then, after removing the glycerine, esterifying the free acids with the desired alcohol. It has been found to be preferable, however, to convert the hydrogenated fat or oil to the lower alkyl esters directly by subjecting the material to alcoholysis. For example, the methyl esters of the fatty acids contained in hydrogenated tallow or cocoanut oil can be prepared efflciently by heating these materials in admixture with methyl alcohol in the presence or absence of a catalyst. The esters are formed in good yields in this way, and can be easily separated from the remainder of the reaction mixture by distilling off the excess methyl alcohol and removing the glycerlne formed in the reaction by a simple washing treatment. The alcoholysis procedure of preparing the esters is of advantage because all of the products of reaction are miscible, whereas when a fat or oil is converted to free fatty acids and .glycerine by hydrolysis, two immiscible phases are formed, which introduces processing difilculties.

The esters, preferably prepared as above described, are sulphonated by bringing them into reactive contact with sulphur trioxide in the presence of liquid sulphur dioxide as the solvent medium. This is preferably carried out by dissolving and/or suspending the esters in liquid sulphur dioxide, and then introducing sulphur trioxide, which. is conveniently in solution in liquid sulphur dioxide, into the resulting solution or suspension. At the completion of the sulphonation, the sulphonation derivatives are recovered from the remainder of the reaction mixture. as such, or in admixture with sulphates. For example, the liquid sulphur dioxide may be distilled off and condensed for use in a succeeding run of the process.

The sulphonation derivatives prepared in this way are alpha-sulphonic acid derivatives oi the saturated higher fatty acids whose esters were employed as the starting materials. The sulphonation derivatives are predominantly in the form of the free acids (or anhydrides). The mixture obtained after distilling of! sulphur dioxide also contains a lower alkyl sulphate in which the alkyl radical corresponds to the alkyl radical of the ester used as the starting material, and a proportion of sulphuric acid resulting from a reaction between iulphur trioxide and water form during the sulphonation. Since the sulphonation derivatives are preferably employed in the form of their partially or wholly neutralized salts, this mixture is treated so as to neutralize the free fatty acids contained therein. To this end the reaction mixture is preferably dissolved in a minimum of water, residual sulphur dioxide is removed as by heating or by passing air or steam through the solution, and the desired neutralizing material is introduced into the solution. At this stage, the alkyl sulphate; e. g., methyl sulphate, is hydrolyzed to the corresponding alcohol and the sulphate of the neutralizing agent. The

, alcohol is preferably distilled off and may be recovered for reuse in the alcoholysis step when this forms a part of the process. After the removal of the alcohol, if the partially neutralized salts have been prepared, these salts may be precipitated from the solution and recovered by filtration: or if the partially or wholly neutralized salts have been prepared, the solution (or slurry) may be dried, as by means of a spray or rotary drum drier, to form a dry product containing salts of alpha-sulphonic acid derivatives of saturated higher fatty acids admixed with a proportion of the sulphate of the neutralizing agent. The sulphate present appears to improve the valuable properties of the product. If desired, salts (in addition to the sulphate formed in the reaction) such as, for example, sodium sulphate, ammonium sulphate, monosodium phosphate, disodium phosphate, sodium tetraborate, sodium silicate, and sodium sesquicarbonate can be added to the product. Also, in certain cases it may be found of advantage to combine the dry product with other detergents and/or wetting agents, suchas ordinary soaps and other sulphonated products.

As previously pointed out. the suiphonation reaction mixtures 01' the present process preferaoiy should contain not more than three per cent of water based on the weight of sulphur trioxide used. It should be noted in this connection that the results obtained in several reactions in which increasing quantities of water are present will vary in degree. The principal eflect noted through increase in the amount of water present in the reaction mixture is a rapid falling oil in the yield of the desired sulphonation derivatives. While it is often the case that by carrying out a process in the presence of a relatively large amount of water and under normal sulphonating conditions, a product of good color is obtained, the yields are so low as to make such a process economically unsound. Further, it a reaction is carried out in the presence of a proportion of water such that, it normal sulphonating conditions were maintained a low yield of a product of good color would be obtained, and the sulphonating conditions are made more vigorous so as to increase the yield, it has been found that a product of poor color is obtained. Thus, the color oi this product (which is indicative of the amount of undesirable by-products present therein) is decidedly inferior to the color of a product obtainable in the same yields using less vigorous sulphonating conditions and carrying out thzreaction in the presence of a smaller proportion of water. In general, it has been found that ii the reaction is carried out in the presence of about three per cent of water based on the weight of sulphur trioxide used, a fair yield of an excellent product may be obtained under normal sulphoriating conditions and a good yield of a reasonably satisfactory product can be obtained under vigorous sulphonating conditions. However, as noted above, it is generally preferable to reduce the water content to one per cent or lower, based on the weight of sulphur trioxide used, sincewith this amount of water present an excellent yield of a product of good color can be obtained under normal sulphonating conditions. In stating that the reaction is carried out under substantially anhydrous conditions, it will be understood that it is meant that 'the reaction mixture contains one per cent or less of water based on the weight of sulphur trioxide used.

In order that the inventionmay be more fully understood, reference should be had to the following specific examples in which are disclosed processes coming within the scope of the present invention. It will be understood that these examples are given for illustrative purposes merely and are not intended as limitatior l of the invention. The parts are by weight and the temperatures are in degrees centigrade.

Example 1.100 parts of hydrogenated cocoa-.

nut oil (prepared by reacting cocoanut oil with hydrogen at an elevated temperature and pressure in the presence of a nickel catalyst) and 48 parts of methyl alcohol are agitated together in a closed vessel for three hours at a temperature of about 200. The excess methyl alcohol is removed from the reaction mixture by distillation at atmospheric pressure leaving a mixture consisting essentially of the methyl esters oi the saturated higher fatty acids of the glycerides oi the hydrogenated cocoanut oil, and glycerine. The glycerine is removed by washing with water. In order to prepare the methyl esters in purified condition, they are then distilled under a vacuum. The esters prepared in thii substantially i'ree irom fatty acids. 10 the esters are introduced into 3000 part: sulphur dioxide in a vessel provided wi ing means. 100 parts oi sulphur trioxid tion in 1000 parts of liquid sulphur di then added, the vessel is closed, and th! mixture so formed is maintained at abo a period or time'sumcient to complete phonation. The vessel is then opened the sulphur dioxide is distilled oil. ant mainder oi the mixture is introduced ii The resulting aqueous mixture is heat move residual sulphur dioxide and an solution containing sumcient sodium 1 to bring the pH of the solution to 7 thereby neutralizing the sulphonation d and free acid contained in the mixture.

tralized mixture is then evaporated tc whereby there is obtained a dry prod prising essentially the sodium salts of ti sulphonic acid derivatives of the saturat fatty acids whose methyl esters were to sulphonation. This dry product has detergent, wetting, and the like propert;

Erample 2.-4.3 parts of methyl laura rifled condition containing less than five of esters of unsaturated higher fatty sulphonated with 4.8 parts of sulphur ti solution in about 143 parts of liquid sulpI ide for a period or about 24 hours at rc perature (about 25). The alpha-sulph derivative of lauric acid is formed as a this treatment. This derivative is separz the remainder of the reaction mixtur neutralized with ammonia to form the um salt which is a valuable detergent an agent.

In preparing products for use as deter wetting agents and the like in accords the procedure of the above examples an procedures, additional salts may be ad ing the neutralization and drying site; up to 20 to 50 per cent by weight of phonated compound) or, if desired, an sulphur trioxide over that required in phonation may be used and neutralied alkaline material (e. g., a caustic alkal monia) to form in situ a salt constltutin By proceeding in accordance with th of the present invention, as illustrated ii amples, sulphonation derivatives oi a wid of saturated higher fatty acids may be by replacing the ester and oil disclose examples with any or the esters or fats of the classes herein disclosed: e. g., ar esters or fats and oils specifically rei above. Thus, in place of the hydrogen coanut oil used in Example 1, there may any other hydrogenated fat or oil subs free from hydroxyl-containing fatty a1 cals; hydrogenated tallow, for example, found to be well adapted for use in the oi this example. Also, in place of the m cohol employed for forming the esters example, there may be used any other 11 phatic alcohol, e. g., one of those in above. For economic and technical reaso ever. it is preferred to employ methyl al ethyl alcohol in this reaction.

In place of the neutralizing agents these examples, there may be used any I kaline material capable oi reacting wit phonic acid group. Thus, sodium carbor tassium carbonate, potassium hydroxi.

' iconic, and methylaminc, for example, can be used for this purpose.

The amount of sulphur trioxide used in the process can be varied within relatively wide limits, but in order to produce satisfactory yields of the desired products, it should not be reduced below three mois for each moi of the saturated fatty acid ester or esters subjected to treatment. I'lor most emcient operation. it is preferred to employ from three to four mole of sulphur trioxide for each mol of the saturated fatty acid ester. As indicated above, however. an excess of sulphur trioxide ordinarily does not have a critical effect on the operativeness of the process and, in some cases where it is desired to form a sulphate in situ, it is of advantage. With respect to the amount of liquid sulphur dioxide required as the solvent medium, it will be understood that this amount is dependent in large measure on the solubility in this medium of the particular sat-- urated fatty acid ester or mixture of esters used as the starting material in the process. 7

As appears from the examples, the sulphonation reaction can be carried out at ordinary temperatures and because of simplicity of operation,

such temperatures are usually employed. If desired, however. a higher or lower temperature can be used; e. g., temperatures varying from to C. are suitable. The time required for the sulphonation reaction is also a variable factor, being dependent upon the specific saturated fatty acid ester or esters subjected to treatment, the apparatus employed, the temperature, and other conditions. Under ordinary conditions of operation. a reaction period of from three to twenty hours is sufficient to complete the sulphonatlon.

In the appended claims where an ester of a saturated higher fatty acid is referred to, it will be understood this term is intended to include mixtures of such esters as well as single esters.

Since certain changes may be made in the above process without departing from the scope of the invention, the above description should be interpreted as illustrative and not in a limiting sense.

I claim:

1. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatty acids which comprises sulphonating a lower alkyl ester of a saturated higher fatty acid with sulphur trioxide in the presence of liquid sulphur dioxide.

2. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatty acids which comprises sulphonating a lower alkyl ester of a saturated higher fatty acid containing from 8 to 24 carbon atoms and containing not substantially more than ten per cent of esters of unsaturated higher fatty acids with sulphur trioxide in the presence of liquid sulphur dioxide.

3. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatty acids which comprises sulphonating a lower alkyl ester of a saturated higher fatty acid containing from 8 to 24 carbon atoms and containing not substantially more than ten per cent of esters of unsaturated higher fatty acids with sulphur trioxide in a reaction mixture in which liquid sulphur dioxide is the solvent medium, said reaction mixture containing not more than three per cent of water based on the weight of suiphur trioxide used in the reaction.

4. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatty acids which comprises sulphonating a lower aikyi ester of a saturated higher fatty acid containing from 14 to 18 carbon atoms and conteining not substantially more than five per cent of esters of unsaturated higher fatty acids with sulphur trioxide in the presence of liquid sulphur dioxide under substantially anhydrous conditions.

5. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatty acids which comprises sulphonating a lowor alkyl ester of a saturated higher fatty acid containing not substantially more than five per cent of esters of unsaturated higher fatty acids with three to four mols of sulphur trioxide for each mol of said lower alkyl ester in the presence of liquid sulphur dioxide under substantially anhydrous conditions.

6. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatty acids which comprises sulphonating a lower alkyi ester of a saturated higher fatty acid selected from the group consisting of the methyl and ethyl esters of said acid containing not substantially more than ten per cent of esters of unsaturated higher fatty acids with sulphur trioxide in the presence of liquid sulphur dioxide. 7. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatty acids which comprises sulphonating a lower alkyl ester of a saturated higher fatty acid selected from the group consisting of the methyl and ethyl esters and containing not substantially more than five per cent of esters of unsaturated higher fatty acids with sulphur trioxide in the presence of liquid sulphur dioxide under substantially anhydrous conditions.

8. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatty acids which comprises sulphonating the methyl ester of a saturated higher fatty acid containing from 8 to 24 carbon atoms and containing not substantially more than five per cent of esters of unsaturated higher fatty acids with sulphur trioxide in a reaction mixture in which liquid sulphur dioxide is the solvent medium, said reaction mixture containing not more than three per cent of water based on the weight of the sulphur trioxide used in the reaction. 1

9. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatty acids which comprises sulphonating the methyl ester of a saturated higher fatty acid containing from 8 to 24 carbon atoms and containing not substantially more than five per cent of esters of unsaturated higher fatty acids with sulphur trioxide in the presence of liquid sulphur dioxide under substantially anhydrous conditions to form the alpha-sulphonic acid derivative of the corresponding saturated higher fatty acid, recovering said alpha-sulphonic acid derivative, and neutralizing said derivative.

10. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatt; acids which comprises hydrogenating a material selected from the group consisting of the naturally occurring fats and oils substantially free from hydroxyi-containing fatty acid radicals, subjecting the hydrogenated material to aicoholysis with a lower aliphatic alcohol to form lower alkyl esters of the fatty acid radicals contained in said material, and sulphonating said lower alkyl esters with sulphur trioxide in the presence of liquid sulphur dioxide under substantially anhydrous conditions, whereby there Mi v is obtained a mixture comprising the alphasulbhcnic acid derivatives of the saturated higher fatty acids contained in said hydrogenated material.

11. The process for the preparation of alphasulphonic acid derivatives of saturated higher fatty acids which comprises hydrogenating a material selected from the group consisting of the naturally occurring fats and oils substantially free from hydroxyl-containlng fatty acid radicals, subjecting the hydrogenated material to ialcoholysis with methyl alcohol to 10m methyl said derivatives.

' WENDEIL W. MOYER. 

